#include <stdio.h>
int main(void){
    double x,y;
    printf("Enter x:");
    scanf("%lf", &x);
    if(x<0){
        y = 0;
    }else if(x<=15){
        y = 4 * x / 3;
    }else{
        y = 2.5 * x - 10.5;
    }
    printf("f(%.2f) = %.2f\n", x, y);
    return 0;
}